服务发现失败了android蓝牙(Service discovery failed android bluetooth)
我正在开发一个代码，用于与Micromax Tab的自定义蓝牙电路进行通信。 直到套接字创建它工作正常。 但是，当我尝试连接时，无法说服务发现失败或主机已关闭。 我尝试了所有可能提到相同问题的帖子。 但最终得到同样的错误。 我试图改变UUID，但没有任何作用。 有什么线索吗？ 以下是我的代码：
final BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); if (mBluetoothAdapter == null) { Toast.makeText(this, "Bluetooth not found",Toast.LENGTH_LONG).show(); } if (!mBluetoothAdapter.isEnabled()) { Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT); } Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices(); // If there are paired devices if (pairedDevices.size() > 0) { // Loop through paired devices for (BluetoothDevice device : pairedDevices) { // Add the name and address to an array adapter to show in a ListView if(device.getName().equals("linvor")) { mmDevice = device; Toast.makeText(this, "Name: " + device.getName() + " And Address: " + device.getAddress(),Toast.LENGTH_LONG).show(); } } } mBluetoothAdapter.cancelDiscovery(); BluetoothSocket tmp = null; // UUID uuid = UUID.fromString("00001105-0000-1000-8000-00805F9B34FB"); // MY_UUID is the app's UUID string, also used by the server code // tmp = mmDevice.createRfcommSocketToServiceRecord(uuid); Method m = null; try { m = mmDevice.getClass().getMethod("createRfcommSocket", new Class[] {int.class}); try { tmp = (BluetoothSocket) m.invoke(mmDevice, 1); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } } catch (NoSuchMethodException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } try { tmp = (BluetoothSocket) m.invoke(mmDevice, 1); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } Toast.makeText(getBaseContext(), "Created socket",Toast.LENGTH_LONG).show(); mmSocket = tmp; mBluetoothAdapter.cancelDiscovery(); Toast.makeText(getBaseContext(), "Discovery cancelled",Toast.LENGTH_LONG).show(); try { // Connect the device through the socket. This will block // until it succeeds or throws an exception mmSocket.connect(); Toast.makeText(getBaseContext(), "Connected",Toast.LENGTH_LONG).show(); } catch (IOException e1) { // Unable to connect; close the socket and get out Toast.makeText(getBaseContext(), e1.getMessage(),Toast.LENGTH_LONG).show(); try { mmSocket.close(); } catch (IOException e) { Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } }I am developing a code to communicate to custom bluetooth circuit from Micromax Tab. Till socket creation it works fine. But when i try to connect it fails saying either Service discovery failed or host is down. I tried all the possible posts referring to this topic mentioning same problem. But end up getting same errors. I tried to change UUID but nothing works. Any clues? Below is my code:
final BluetoothAdapter mBluetoothAdapter = BluetoothAdapter.getDefaultAdapter(); if (mBluetoothAdapter == null) { Toast.makeText(this, "Bluetooth not found",Toast.LENGTH_LONG).show(); } if (!mBluetoothAdapter.isEnabled()) { Intent enableBtIntent = new Intent(BluetoothAdapter.ACTION_REQUEST_ENABLE); startActivityForResult(enableBtIntent, REQUEST_ENABLE_BT); } Set<BluetoothDevice> pairedDevices = mBluetoothAdapter.getBondedDevices(); // If there are paired devices if (pairedDevices.size() > 0) { // Loop through paired devices for (BluetoothDevice device : pairedDevices) { // Add the name and address to an array adapter to show in a ListView if(device.getName().equals("linvor")) { mmDevice = device; Toast.makeText(this, "Name: " + device.getName() + " And Address: " + device.getAddress(),Toast.LENGTH_LONG).show(); } } } mBluetoothAdapter.cancelDiscovery(); BluetoothSocket tmp = null; // UUID uuid = UUID.fromString("00001105-0000-1000-8000-00805F9B34FB"); // MY_UUID is the app's UUID string, also used by the server code // tmp = mmDevice.createRfcommSocketToServiceRecord(uuid); Method m = null; try { m = mmDevice.getClass().getMethod("createRfcommSocket", new Class[] {int.class}); try { tmp = (BluetoothSocket) m.invoke(mmDevice, 1); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } } catch (NoSuchMethodException e1) { // TODO Auto-generated catch block e1.printStackTrace(); } try { tmp = (BluetoothSocket) m.invoke(mmDevice, 1); } catch (IllegalArgumentException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (IllegalAccessException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } catch (InvocationTargetException e) { // TODO Auto-generated catch block Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } Toast.makeText(getBaseContext(), "Created socket",Toast.LENGTH_LONG).show(); mmSocket = tmp; mBluetoothAdapter.cancelDiscovery(); Toast.makeText(getBaseContext(), "Discovery cancelled",Toast.LENGTH_LONG).show(); try { // Connect the device through the socket. This will block // until it succeeds or throws an exception mmSocket.connect(); Toast.makeText(getBaseContext(), "Connected",Toast.LENGTH_LONG).show(); } catch (IOException e1) { // Unable to connect; close the socket and get out Toast.makeText(getBaseContext(), e1.getMessage(),Toast.LENGTH_LONG).show(); try { mmSocket.close(); } catch (IOException e) { Toast.makeText(getBaseContext(), e.getMessage(),Toast.LENGTH_LONG).show(); } }
原文：https://stackoverflow.com/questions/17989555
最满意答案
我不知道你问题的所有细节，但我的直觉是你可能会在这里思考问题。 您计划在此数据结构中存储多少个对象？ 如果您要在此处存储大量数据，我建议您使用实际数据库而不是数据结构。 您在此处描述的操作类型是关系数据库擅长的事物的经典示例。 MySQL和PostgreSQL是大规模关系数据库的例子，它们可以在睡眠中做这种事情。 如果你想要一些重量较轻的SQLite可能会引起人们的兴趣。
如果您没有需要存储在此数据结构中的大量数据，我建议您保持简单，只有当您确定它不够快，无法满足您的需求时才进行优化。 作为第一个镜头，我建议使用java内置的List界面来存储你的人物，并使用Map来存储组。 你可以这样做：
// Use a list to keep track of People List<Person> myPeople = new ArrayList<Person>(); Person steve = new Person("Steve"); myPeople.add(steve); myPeople.add(new Person("Bob")); // Use a Map to track Groups Map<String, List<Person>> groups = new HashMap<String, List<Person>>(); groups.put("Everybody", myPeople); groups.put("Developers", Arrays.asList(steve)); // Does a group contain everybody? groups.get("Everybody").containsAll(myPeople); // returns true groups.get("Developers").containsAll(myPeople); // returns false这绝对不是最快的选择，但如果你没有大量的人来跟踪，你可能甚至不会注意到任何性能问题。 如果您确实有一些特殊条件会使常规列表和地图的使用速度变得不可行，请发布它们，我们可以根据这些条件提出建议。
编辑：
在阅读您的评论后，我似乎在第一次浏览时误读了您的问题。 看起来你对将人群映射给人们并不是那么感兴趣，而是将人们映射到群组。 你可能想要的是更像这样的东西：
Map<Person, List<String>> associations = new HashMap<Person, List<String>>(); Person steve = new Person("Steve"); Person ed = new Person("Ed"); associations.put(steve, Arrays.asList("Everybody", "Developers")); associations.put(ed, Arrays.asList("Everybody")); // This is the tricky part boolean sharesGroups = checkForSharedGroups(associations, Arrays.asList(steve, ed));那么如何实现checkForSharedGroups方法呢？ 在你的情况下，因为围绕这个的数字非常低，我只是尝试一下天真的方法并从那里开始。
public boolean checkForSharedGroups( Map<Person, List<String>> associations, List<Person> peopleToCheck){ List<String> groupsThatHaveMembers = new ArrayList<String>(); for(Person p : peopleToCheck){ List<String> groups = associations.get(p); for(String s : groups){ if(groupsThatHaveMembers.contains(s)){ // We've already seen this group, so we can return return false; } else { groupsThatHaveMembers.add(s); } } } // If we've made it to this point, nobody shares any groups. return true; }这种方法在大型数据集上可能没有很好的性能，但它很容易理解。 因为它封装在它自己的方法中，所以如果事实证明你需要更好的性能，它也应该很容易更新。 如果你确实需要提高性能，我会考虑覆盖Person的equals方法 ，这将使关联映射中的查找更快。 从那里你也可以查看自定义类型而不是组的字符串，也可以使用重写的equals方法。 这将大大加快上面使用的包含方法。
我不太关心性能的原因是，就算法而言，你提到的数字并不是那么大。 因为此方法在找到两个匹配组后立即返回，在最坏的情况下，您将调用ArrayList.contains多次等于存在的组数。 在最好的情况下，它只需要被调用两次。 如果你经常非常频繁地调用checkForSharedGroups，那么性能可能只是一个问题，在这种情况下，你可能最好找到一种不经常调用它的方法，而不是优化方法本身。
I don't know all of the details of your problem, but my gut instinct is that you may be over thinking things here. How many objects are you planning on storing in this data structure? If you have really large amounts of data to store here, I would recommend that you use an actual database instead of a data structure. The type of operations you are describing here are classical examples of things that relational databases are good at. MySQL and PostgreSQL are examples of large scale relational databases that could do this sort of thing in their sleep. If you'd like something lighter-weight SQLite would probably be of interest.
If you do not have large amounts of data that you need to store in this data structure, I'd recommend keeping it simple, and only optimizing it when you are sure that it won't be fast enough for what you need to do. As a first shot, I'd just recommend using java's built in List interface to store your people and a Map to store groups. You could do something like this:
// Use a list to keep track of People List<Person> myPeople = new ArrayList<Person>(); Person steve = new Person("Steve"); myPeople.add(steve); myPeople.add(new Person("Bob")); // Use a Map to track Groups Map<String, List<Person>> groups = new HashMap<String, List<Person>>(); groups.put("Everybody", myPeople); groups.put("Developers", Arrays.asList(steve)); // Does a group contain everybody? groups.get("Everybody").containsAll(myPeople); // returns true groups.get("Developers").containsAll(myPeople); // returns falseThis definitly isn't the fastest option available, but if you do not have a huge number of People to keep track of, you probably won't even notice any performance issues. If you do have some special conditions that would make the speed of using regular Lists and Maps unfeasible, please post them and we can make suggestions based on those.
EDIT:
After reading your comments, it appears that I misread your issue on the first run through. It looks like you're not so much interested in mapping groups to people, but instead mapping people to groups. What you probably want is something more like this:
Map<Person, List<String>> associations = new HashMap<Person, List<String>>(); Person steve = new Person("Steve"); Person ed = new Person("Ed"); associations.put(steve, Arrays.asList("Everybody", "Developers")); associations.put(ed, Arrays.asList("Everybody")); // This is the tricky part boolean sharesGroups = checkForSharedGroups(associations, Arrays.asList(steve, ed));So how do you implement the checkForSharedGroups method? In your case, since the numbers surrounding this are pretty low, I'd just try out the naive method and go from there.
public boolean checkForSharedGroups( Map<Person, List<String>> associations, List<Person> peopleToCheck){ List<String> groupsThatHaveMembers = new ArrayList<String>(); for(Person p : peopleToCheck){ List<String> groups = associations.get(p); for(String s : groups){ if(groupsThatHaveMembers.contains(s)){ // We've already seen this group, so we can return return false; } else { groupsThatHaveMembers.add(s); } } } // If we've made it to this point, nobody shares any groups. return true; }This method probably doesn't have great performance on large datasets, but it is very easy to understand. Because it's encapsulated in it's own method, it should also be easy to update if it turns out you need better performance. If you do need to increase performance, I would look at overriding the equals method of Person, which would make lookups in the associations map faster. From there you could also look at a custom type instead of String for groups, also with an overridden equals method. This would considerably speed up the contains method used above.
The reason why I'm not too concerned about performance is that the numbers you've mentioned aren't really that big as far as algorithms are concerned. Because this method returns as soon as it finds two matching groups, in the very worse case you will call ArrayList.contains a number of times equal to the number of groups that exist. In the very best case scenario, it only needs to be called twice. Performance will likely only be an issue if you call the checkForSharedGroups very, very often, in which case you might be better off finding a way to call it less often instead of optimizing the method itself.
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